Just like medical school, getting accepted into nursing school doesn't mean she will ever be licensed as a nurse. Yes, it varies from state to state, but sometimes nursing boards are even harder on past criminal convictions than medical boards. I have heard of more than one nurse, who got a BSN, and then could never actually practice as a nurse.
I completely disagree with people telling you to consider other healthcare careers. Your convictions, especially the DV conviction, are likely to be a problem getting licensed in any healthcare career
I know it sucks. Everyone makes mistakes in life, and you have done a great job in correcting the mistakes you've made. But I think you should seriously consider another field. You probably really need to do a career assessment, and talk with a career counselor, to see where to go from.
You mention not wanting to restart your bachelor's, but many of your core bachelor's classes will transfer. Yes, if you completely change majors, you make have to do an extra 1 - 2 years.....but this will be far preferable to getting an MD, and then never being able to practice as a doctor.
Taking the boards isn't the problem, its getting licensed. She can pass all the board exams and still not get licensed because of her criminal convictions. That will not change regardless of where she went to school at.
This has not been clear in your OP. How far along are you in your bachelor's degree, and what is your actual major? "Pre-med" is usually not an actual major.
There are no hard and fast answers. Some people can be taking drugs under prescription and be quite stable and not impaired by those drugs. Others could be taking those same drugs under prescription and be impaired. Generally speaking, taking drugs acutely (like for a cold) are more likely to impair someone's judgement, then taking the same drug chronically. Yes, people have been convicted of DWI because they took Benadryl. *Any* drug, whether legal or not, that influences your behavior as an individual, can lead to a DWI conviction (or get you in trouble with your state board for practicing while taking it.)